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• Building a News-feed that comprises posts "created by user's connections" && "on the topics user is following"

  - by aklin81

  I am working on a project of Questions & Answers website that allows a user to follow questions on certain topics from his network. A user's news-feed wall comprises of only those questions that have been posted by his connections and tagged on the topics that he is following(his expertise topics). I am confused what database's datamodel would be most fitting for such an application. The project needs to consider the future provisions for scalability and high performance issues. I have been looking at Cassandra and MySQL solutions as of now. After my study of Cassandra I realized that Simple news-feed design that shows all the posts from network would be easy to design using Cassandra by executing fast writes to all followers of a user about the post from user. But for my kind of application where there is an additional filter of 'followed topics', (ie, the user receives posts "created by his network" && "on topics user is following"), I could not convince myself with a good schema design in Cassandra. I hope if I missed something because of my short understanding of cassandra, perhaps, can you please help me out with your suggestions of how this news-feed could be implemented in Cassandra ? Looking for a great project with Cassandra ! Edit: There are going to be maximum 5 tags allowed for tagging the question (ie, max 5 topics can be tagged on a question).

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• How do I access data within this multidimensional array?

  - by dmanexe

  I have this array: $items_pool = Array ( [0] => Array ( [id] => 1 [quantity] => 1 ) [1] => Array ( [id] => 2 [quantity] => 1 ) [2] => Array ( [id] => 72 [quantity] => 6 ) [3] => Array ( [id] => 4 [quantity] => 1 ) [4] => Array ( [id] => 5 [quantity] => 1 ) [5] => Array ( [id] => 7 [quantity] => 1 ) [6] => Array ( [id] => 8 [quantity] => 1 ) [7] => Array ( [id] => 9 [quantity] => 1 ) [8] => Array ( [id] => 19 [quantity] => 1 ) [9] => Array ( [id] => 20 [quantity] => 1 ) [10] => Array ( [id] => 22 [quantity] => 1 ) [11] => Array ( [id] => 29 [quantity] => 0 ) ) I'm trying to loop through this array and perform a conditional based on $items_pool[][id]'s value. I want to then report back TRUE or NULL/FALSE, so I'm just testing the presence of to be specific.

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• Locking behaviour is different via network shares

  - by MattH

  I have been trying to lock a file so that other cloned services cannot access the file. I then read the file, and then move the file when finished. The Move is allowed by using FileShare.Delete. However in later testing, we found that this approach does not work if we are looking at a network share. I appreciate my approach may not have been the best, but my specific question is: Why does the below demo work against the local file, but not against the network file? The more specific you can be the better, as I've found very little information in my searches that indicates network shares behave differently to local disks. string sourceFile = @"C:\TestFile.txt"; string localPath = @"C:\MyLocalFolder\TestFile.txt"; string networkPath = @"\\MyMachine\MyNetworkFolder\TestFile.txt"; File.WriteAllText(sourceFile, "Test data"); if (!File.Exists(localPath)) File.Copy(sourceFile, localPath); foreach (string path in new string[] { localPath, networkPath }) { using (FileStream fsLock = File.Open(path, FileMode.Open, FileAccess.ReadWrite, (FileShare.Read | FileShare.Delete))) { string target = path + ".out"; File.Move(path, target); //This is the point of failure, when working with networkPath if (File.Exists(target)) File.Delete(target); } if (!File.Exists(path)) File.Copy(sourceFile, path); }

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• DSA signature verification input

  - by calccrypto

  What is the data inputted into DSA when PGP signs a message? From RFC4880, i found A Signature packet describes a binding between some public key and some data. The most common signatures are a signature of a file or a block of text, and a signature that is a certification of a User ID. im not sure if it is the entire public key, just the public key packet, or some other derivative of a pgp key packet. whatever it is, i cannot get the DSA signature to verify here is a sample im testing my program on: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 abcd -----BEGIN PGP SIGNATURE----- Version: BCPG v1.39 iFkEARECABkFAk0z65ESHGFiYyAodGVzdCBrZXkpIDw+AAoJEC3Jkh8+bnkusO0A oKG+HPF2Qrsth2zS9pK+eSCBSypOAKDBgC2Z0vf2EgLiiNMk8Bxpq68NkQ== =gq0e -----END PGP SIGNATURE----- Dumped from pgpdump.net Old: Signature Packet(tag 2)(89 bytes) Ver 4 - new Sig type - Signature of a canonical text document(0x01). Pub alg - DSA Digital Signature Algorithm(pub 17) Hash alg - SHA1(hash 2) Hashed Sub: signature creation time(sub 2)(4 bytes) Time - Mon Jan 17 07:11:13 UTC 2011 Hashed Sub: signer's User ID(sub 28)(17 bytes) User ID - abc (test key) <> Sub: issuer key ID(sub 16)(8 bytes) Key ID - 0x2DC9921F3E6E792E Hash left 2 bytes - b0 ed DSA r(160 bits) - a1 be 1c f1 76 42 bb 2d 87 6c d2 f6 92 be 79 20 81 4b 2a 4e DSA s(160 bits) - c1 80 2d 99 d2 f7 f6 12 02 e2 88 d3 24 f0 1c 69 ab af 0d 91 -> hash(DSA q bits) and the public key for it is: -----BEGIN PGP PUBLIC KEY BLOCK----- Version: BCPG v1.39 mOIETTPqeBECALx+i9PIc4MB2DYXeqsWUav2cUtMU1N0inmFHSF/2x0d9IWEpVzE kRc30PvmEHI1faQit7NepnHkkphrXLAoZukAoNP3PB8NRQ6lRF6/6e8siUgJtmPL Af9IZOv4PI51gg6ICLKzNO9i3bcUx4yeG2vjMOUAvsLkhSTWob0RxWppo6Pn6MOg dMQHIM5sDH0xGN0dOezzt/imAf9St2B0HQXVfAAbveXBeRoO7jj/qcGx6hWmsKUr BVzdQhBk7Sku6C2KlMtkbtzd1fj8DtnrT8XOPKGp7/Y7ASzRtBFhYmMgKHRlc3Qg a2V5KSA8PohGBBMRAgAGBQJNM+p5AAoJEC3Jkh8+bnkuNEoAnj2QnqGtdlTgUXCQ Fyvwk5wiLGPfAJ4jTGTL62nWzsgrCDIMIfEG2shm8bjMBE0z6ngQAgCUlP7AlfO4 XuKGVCs4NvyBpd0KA0m0wjndOHRNSIz44x24vLfTO0GrueWjPMqRRLHO8zLJS/BX O/BHo6ypjN87Af0VPV1hcq20MEW2iujh3hBwthNwBWhtKdPXOndJGZaB7lshLJuW v9z6WyDNXj/SBEiV1gnPm0ELeg8Syhy5pCjMAgCFEc+NkCzcUOJkVpgLpk+VLwrJ /Wi9q+yCihaJ4EEFt/7vzqmrooXWz2vMugD1C+llN6HkCHTnuMH07/E/2dzciEYE GBECAAYFAk0z6nkACgkQLcmSHz5ueS7NTwCdED1P9NhgR2LqwyS+AEyqlQ0d5joA oK9xPUzjg4FlB+1QTHoOhuokxxyN =CTgL -----END PGP PUBLIC KEY BLOCK----- the public key packet of the key is mOIETTPqeBECALx+i9PIc4MB2DYXeqsWUav2cUtMU1N0inmFHSF/2x0d9IWEpVzEkRc30PvmEHI1faQi t7NepnHkkphrXLAoZukAoNP3PB8NRQ6lRF6/6e8siUgJtmPLAf9IZOv4PI51gg6ICLKzNO9i3bcUx4ye G2vjMOUAvsLkhSTWob0RxWppo6Pn6MOgdMQHIM5sDH0xGN0dOezzt/imAf9St2B0HQXVfAAbveXBeRoO 7jj/qcGx6hWmsKUrBVzdQhBk7Sku6C2KlMtkbtzd1fj8DtnrT8XOPKGp7/Y7ASzR in radix 64 i have tried many different combinations of sha1(< some data + 'abcd'),but the calculated value v never equals r, of the signature i know that the pgp implementation i used to create the key and signature is correct. i also know that my DSA implementation and PGP key data extraction program are correct. thus, the only thing left is the data to hash. what is the correct data to be hashed?

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• MS Surface Tag Visualizer steals contact events

  - by Isak Savo

  I'm struggling with the TagVisualizer control on an MS Surface project. In theory the control seems great, allowing you to respond to input from real world physical objects The problem is that the control will cover the entire screen (since I want to capture tags on the entire screen) and as such, no other controls in my app will receive the touch events. (Unless, they are direct ascendants in the visual tree). In my app, I want to have a "layer" type of a approach, where each layer can respond to (contact) input: Window `- Grid `- LayersPanel `- TagVisualizer `- Layer 1 `- Layer 2 `- Layer 3 `- Layer 4 Now it doesn't matter where I put the tag visualizer, it's always going to steal contact events from all or some of the other layers. (due to the nature of RoutedEvents) To me, it seems like the control is completely useless in practice as it will always interfere with your application's other controls. What am I missing here? So my questions are: Any suggestions on how to work around this? Has anyone used TagVisualizers in a similar scenario? If so, how did you solve this? By the way, the layers all work fine, since they will only steal events that are directly on top of their sub elements (the rest of the layer is invisible to hit testing)

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• Autocomplete and IE7 - slowness, sluggishness as overall pagesize grows?

  - by wchrisjohnson

  Hi, I have the autocomplete plugin (http://bassistance.de/jquery-plugins/jquery-plugin-autocomplete/, version 1.1 and 1.0.2) on a project to add pieces of "equipment" to a "project". On a fresh project the plugin works great; the data returned from the database comes back FAST, you can scroll the list fast, and can select an item and move on to the next one. Once I have a project established with equipment on it, and I go to add equipment, the performance is pretty bad. It takes 4-5 seconds to get the list of data back from the server, scrolling the list is painful, and the cursor takes several seconds to settle on an item. Repainting the page after the list goes away is slow. This is occurring in IE7, latest version. FF3 and Chrome are fine, very snappy. The pagesize is about 40K overall. I'm thinking this is an issue with the IE7 Javascript engine, or an edge case with this plugin and IE7; it works quickly enough in FF3+. I would appreciate any ideas, solutions, known issues, or thoughts on how to more specifically pin this down. I'd love to post sample code, but this is a corporate app, and I'm not how useful it would be given that the server side piece cannot be shown; ie: you can't pull it down and test it like a self contained piece of code.. Thanks in advance! Chris

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• How to synchronize placing an object in JNDI across processes?

  - by indra

  I am trying to place an object in JNDI, so that only one of the progam should be able to place it in JNDI. is there any global lock that can be used in J2EE environment. Is RMI can be used for this purpose? please provide any reference links. Thanks in advance. Also, what is NameAlreadyBoundexception? I am trying to use it as a method to synchronize, i.e, only one program places it in JNDI and if other trying to bind should get that exception. But when i am testing the multiple binding I am not getting the Exception.And second binding is done. look up is giving the second object bound. here is my code: private static String JNDI_NAME = "java:comp/env/test/something"; public class TestJNDI { private static String JNDI_NAME = "java:comp/env/test/something"; public static void main(String[] args) throws NamingException { Hashtable env = new Hashtable(); env.put(Context.INITIAL_CONTEXT_FACTORY,"weblogic.jndi.WLInitialContextFactory"); env.put(Context.PROVIDER_URL,"t3://127.0.0.1:7001"); Context ctx = new InitialContext(env); System.out.println("Initial Context created"); String obj1 = "obj1"; String obj2 = "obj2"; try{ ctx.bind(JNDI_NAME, obj1); System.out.println("Bind Sucess"); }catch(NameAlreadyBoundException ne ){ // already bound System.out.println("Name already bound"); } ctx.close(); Context ctx2 = new InitialContext(env); try{ // Second binding to the same name not giving the Exception?? ctx2.bind(JNDI_NAME, obj2); System.out.println("Re Bind Sucess"); }catch(NameAlreadyBoundException ne ){ // already bound System.out.println("Name already bound"); } String lookedUp = (String) ctx2.lookup(JNDI_NAME); System.out.println("LookedUp Object"+lookedUp); ctx2.close(); } }

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• Problem with persisting a collection, that references an internal property, at design time in winfor

  - by Jules

  ETA: Jesus, I'm sick of this. This problem was specifically about persisting an interface collection but now on further testing it doesn't work for a normal collection. Here's some even simpler code: Public Class Anger End Class Public Class MyButton Inherits Button Private _Annoyance As List(Of Anger) <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property Annoyance() As List(Of Anger) Get Return _Annoyance End Get End Property Private _InternalAnger As Anger <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property InternalAnger() As Anger Get Return Me._InternalAnger End Get End Property Public Sub New() Me._Annoyance = New List(Of Anger) Me._InternalAnger = New Anger Me._Annoyance.Add(Me._InternalAnger) End Sub End Class The designer screws up the persistence code in the same way as the original problem. ---- Original Problem The easiest way to explain this problem is to show you some code: Public Interface IAmAnnoyed End Interface Public Class IAmAnnoyedCollection Inherits ObjectModel.Collection(Of IAmAnnoyed) End Class Public Class Anger Implements IAmAnnoyed End Class Public Class MyButton Inherits Button Private _Annoyance As IAmAnnoyedCollection <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property Annoyance() As IAmAnnoyedCollection Get Return _Annoyance End Get End Property Private _InternalAnger As Anger <DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _ Public ReadOnly Property InternalAnger() As Anger Get Return Me._InternalAnger End Get End Property Public Sub New() Me._Annoyance = New IAmAnnoyedCollection Me._InternalAnger = New Anger Me._Annoyance.Add(Me._InternalAnger) End Sub End Class And this is the code that the designer generates: Private Sub InitializeComponent() Dim Anger1 As Anger = New Anger Me.MyButton1 = New MyButton ' 'MyButton1 ' Me.MyButton1.Annoyance.Add(Anger1) // Should be: Me.MyButton1.Annoyance.Add(Me.MyButton1.InternalAnger) ' 'Form1 ' Me.Controls.Add(Me.MyButton1) End Sub I've added a comment to the above to show how the code should have been generated. Now, if I dispense with the interface and just have a collection of Anger, then it persists correctly. Any ideas?

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• How to specify path for file from different project in WPF?

  - by MartyIX

  Hello, I've got two projects in WPF and one project is the main one and the second one is just for testing (it uses files of the main project - files are added via Project - add - Existing items... - selected file - add as link so that the file is only in the main project really). Folders with projects are these: C:\Work\...\Projects\Main C:\Work\...\Projects\XXXTestProject where XXX stands for different parts of the Main project which I test separately. I've got the code: <Window x:Class="Sokoban.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:Sokoban" xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase" Title="Window1" Height="559" Width="419"> <Window.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="GameDesk.xaml" /> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </Window.Resources> <Grid> <Rectangle local:GameDeskProperties.FieldSize="30" Name="myrect" Style="{DynamicResource GameDesk}" MouseEnter="Rectangle_MouseEnter" /> </Grid> </Window> ... which should use XAML resources from GameDesk.xaml which is in the main project and it seems that I can't use Pack URI (http://msdn.microsoft.com/en-us/library/aa970069.aspx). How can I specify the file? Should I use absolute path? (C:\Work...\Main\Resources\GameDesk.xaml) Or is there any other way? Thank you for help!

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• C#: Accessing PerformanceCounters for the ".NET CLR Memory category"

  - by Mads Ravn

  I'm trying to access the performance counters located in ".NET CLR Memory category" through C# using the PerformanceCounter class. However a cannot instantiate the categories with what I would expect was the correct category/counter name new PerformanceCounter(".NET CLR Memory", "# bytes in all heaps", Process.GetCurrentProcess().ProcessName); I tried looping through categories and counters using the following code string[] categories = PerformanceCounterCategory.GetCategories().Select(c => c.CategoryName).OrderBy(s => s).ToArray(); string toInspect = string.Join(",\r\n", categories); System.Text.StringBuilder interestingToInspect = new System.Text.StringBuilder(); string[] interestingCategories = categories.Where(s => s.StartsWith(".NET") || s.Contains("Memory")).ToArray(); foreach (string interestingCategory in interestingCategories) { PerformanceCounterCategory cat = new PerformanceCounterCategory(interestingCategory); foreach (PerformanceCounter counter in cat.GetCounters()) { interestingToInspect.AppendLine(interestingCategory + ":" + counter.CounterName); } } toInspect = interestingToInspect.ToString(); But could not find anything that seems to match. Is it not possible to observe these values from within the CLR or am I doing something wrong. The environment, should it matter, is .NET 4.0 running on a 64-bit windows 7 box.

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• Executing remote script - Architecture

  - by Bruno Lee

  Hi, I want to make an application that executes a remote script. The user can create a script (probabily a LUA script) then stores it in the server. Then he can uses an API for execute the script. I was thinking that API could be a webservice. So my questions are: I need high performance to execute the script. So my first choice was LUA script. Someone has another sugestion? Cause I need high perfomance, I was thinking if the webservice is the best solution. Maybe I could create a TCP/IP Windows Service that hold the users request. It is important to say that I will have many user executing scripts at the same time. So I will have a concurrency problem. My scripts will query in a database. I will use Tokyo Cabinet or Tokio Tyrant. I think Tokio Tyrant is the only solution cause I will have many requests. For perfomance, Do I need to make a connection pooling? Is there anyway to share variables between webservices requests? To make the webservice or the Windows service i was thinking to use C++. Can someone help with these questions? thanks

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• Most efficient way to check for DBNull and then assign to a variable?

  - by ilitirit

  This question comes up occasionally but I haven't seen a satisfactory answer. A typical pattern is (row is a DataRow): if (row["value"] != DBNull.Value) { someObject.Member = row["value"]; } My first question is which is more efficient (I've flipped the condition): row["value"] == DBNull.Value; // Or row["value"] is DBNull; // Or row["value"].GetType() == typeof(DBNull) // Or... any suggestions? This indicates that .GetType() should be faster, but maybe the compiler knows a few tricks I don't? Second question, is it worth caching the value of row["value"] or does the compiler optimize the indexer away anyway? eg. object valueHolder; if (DBNull.Value == (valueHolder = row["value"])) {} Disclaimers: row["value"] exists. I don't know the column index of the column (hence the column name lookup) I'm asking specifically about checking for DBNull and then assignment (not about premature optimization etc). Edit: I benchmarked a few scenarios (time in seconds, 10000000 trials): row["value"] == DBNull.Value: 00:00:01.5478995 row["value"] is DBNull: 00:00:01.6306578 row["value"].GetType() == typeof(DBNull): 00:00:02.0138757 Object.ReferenceEquals has the same performance as "==" The most interesting result? If you mismatch the name of the column by case (eg. "Value" instead of "value", it takes roughly ten times longer (for a string): row["Value"] == DBNull.Value: 00:00:12.2792374 The moral of the story seems to be that if you can't look up a column by it's index, then ensure that the column name you feed to the indexer matches the DataColumn's name exactly. Caching the value also appears to be nearly twice as fast: No Caching: 00:00:03.0996622 With Caching: 00:00:01.5659920 So the most efficient method seems to be: object temp; string variable; if (DBNull.Value != (temp = row["value"]) { variable = temp.ToString(); } This was a good learning experience.

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• Avoiding GC thrashing with WSE 3.0 MTOM service

  - by Leon Breedt

  For historical reasons, I have some WSE 3.0 web services that I cannot upgrade to WCF on the server side yet (it is also a substantial amount of work to do so). These web services are being used for file transfers from client to server, using MTOM encoding. This can also not be changed in the short term, for reasons of compatibility. Secondly, they are being called from both Java and .NET, and therefore need to be cross-platform, hence MTOM. How it works is that an "upload" WebMethod is called by the client, sending up a chunk of data at a time, since files being transferred could potentially be gigabytes in size. However, due to not being able to control parts of the stack before the WebMethod is invoked, I cannot control the memory usage patterns of the web service. The problem I am running into is for file sizes from 50MB or so onwards, performance is absolutely killed because of GC, since it appears that WSE 3.0 buffers each chunk received from the client in a new byte[] array, and by the time we've done 50MB we're spending 20-30% of time doing GC. I've played with various chunk sizes, from 16k to 2MB, with no real great difference in results. Smaller chunks are killed by the latency involved with round-tripping, and larger chunks just postpone the slowdown until GC kicks in. Any bright ideas on cutting down on the garbage created by WSE? Can I plug into the pipeline somehow and jury-rig something that has access to the client's request stream and streams it to the WebMethod? I'm aware that it is possible to "stream" responses to the client using WSE (albeit very ugly), but this problem is with requests from the client.

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• Print a string that contains a certain pattern in Java

  - by jjpotter

  I am trying to find a regular expression within a line of a .csv file, so I can eventually save all the matches to another file, and lose all the other junk. So a line in my file might look like: MachineName,User,IP,VariableData,Location The VariableData is what I want to match, and if there's a match, print the line. I am using a pattern for this because I only want 3 out of 10 of variations of VariableData, and out of those 3, they are numbered differently(example, "pc104, pccrt102, pccart65"). I am trying to do this using the Scanner Class and keeping it simple as possible so I can understand it. Here is where I was heading with this...(the pattern isn't complete, just have it like this for testing). import java.io.File; import java.util.Scanner; import java.util.regex.Pattern; public class pcv { public static void main(String[] args) { File myFile = new File("c:\\temp\\report.csv"); Pattern myPat = Pattern.compile("pc"); try{ Scanner myScan = new Scanner(myFile); while(myScan.hasNext()){ if(myScan.hasNext(myPat)){ System.out.println("Test"); } } }catch(Exception e){ } } } This code loops, im guessing the .hasNext() methods are resetting themselves. I've played around with the Matcher class a little bit, but only found a way to match the expression but not get the whole line. My other throught was maybe somehow count the line that contains the pattern, then go back and print the line that corresponds to the counts.

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• Architecture with NHibernate and Repositories

  - by Matthew

  I've been reading up on MVC 2 and the recommended patterns, so far I've come to the conclusion (amongst much hair pulling and total confusion) that: Model - Is just a basic data container Repository - Provides data access Service - Provides business logic and acts as an API to the Controller The Controller talks to the Service, the Service talks to the Repository and Model. So for example, if I wanted to display a blog post page with its comments, I might do: post = PostService.Get(id); comments = PostService.GetComments(post); Or, would I do: post = PostService.Get(id); comments = post.Comments; If so, where is this being set, from the repository? the problem there being its not lazy loaded.. that's not a huge problem but then say I wanted to list 10 posts with the first 2 comments for each, id have to load the posts then loop and load the comments which becomes messy. All of the example's use "InMemory" repository's for testing and say that including db stuff would be out of scope. But this leaves me with many blanks, so for a start can anyone comment on the above?

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• Finding a picture in a picture with java?

  - by tarrasch

  what i want to to is analyse input from screen in form of pictures. I want to be able to identify a part of an image in a bigger image and get its coordinates within the bigger picture. Example: would have to be located in And the result would be the upper right corner of the picture in the big picture and the lower left of the part in the big picture. As you can see, the white part of the picture is irrelevant, what i basically need is just the green frame. Is there a library that can do something like this for me? Runtime is not really an issue. What i want to do with this is just generating a few random pixel coordinates and recognize the color in the big picture at that position, to recognize the green box fast later. And how would it decrease performance, if the white box in the middle is transparent? The question has been asked several times on SO as it seems without a single answer. I found i found a solution at http://werner.yellowcouch.org/Papers/subimg/index.html . Unfortunately its in C++ and i do not understand a thing. Would be nice to have a Java implementation on SO.

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• Why use INCLUDE in a SQL index

  - by StarLite

  I recently encountered an index in a database I maintain that was of the form: CREATE INDEX [IX_Foo] ON [Foo] ( Id ASC ) INCLUDE ( SubId ) In this particular case, the performance problem that I was encountering (a slow SELECT filtering on both Id and SubId) could be fixed by simply moving the SubId column into the index proper rather than as an included column. This got me thinking however that I don't understand the reasoning behind included columns at all, when generally, they could simply be a part of the index itself. Even if I don't particularly care about the items being in the index itself is there any downside to having column in the index rather than simply being included. After some research, I am aware that there are a number of restrictions on what can go into an indexed column (maximum width of the index, and some column types that can't be indexed like 'image'). In these cases I can see that you would be forced to include the column in the index page data. The only thing I can think of is that if there are updates on SubId, the row will not need to be relocated if the column is included (though the value in the index would need to be changed). Is there something else that I'm missing? I'm considering going through the other indexes in the database and shifting included columns in the index proper where possible. Would this be a mistake? I'm primarily interested in MS SQL Server, but information on other DB engines is welcome also.

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• deepcopy and python - tips to avoid using it?

  - by blackkettle

  Hi, I have a very simple python routine that involves cycling through a list of roughly 20,000 latitude,longitude coordinates and calculating the distance of each point to a reference point. def compute_nearest_points( lat, lon, nPoints=5 ): """Find the nearest N points, given the input coordinates.""" points = session.query(PointIndex).all() oldNearest = [] newNearest = [] for n in xrange(nPoints): oldNearest.append(PointDistance(None,None,None,99999.0,99999.0)) newNearest.append(obj2) #This is almost certainly an inappropriate use of deepcopy # but how SHOULD I be doing this?!?! for point in points: distance = compute_spherical_law_of_cosines( lat, lon, point.avg_lat, point.avg_lon ) k = 0 for p in oldNearest: if distance < p.distance: newNearest[k] = PointDistance( point.point, point.kana, point.english, point.avg_lat, point.avg_lon, distance=distance ) break else: newNearest[k] = deepcopy(oldNearest[k]) k += 1 for j in range(k,nPoints-1): newNearest[j+1] = deepcopy(oldNearest[j]) oldNearest = deepcopy(newNearest) #We're done, now print the result for point in oldNearest: print point.station, point.english, point.distance return I initially wrote this in C, using the exact same approach, and it works fine there, and is basically instantaneous for nPoints<=100. So I decided to port it to python because I wanted to use SqlAlchemy to do some other stuff. I first ported it without the deepcopy statements that now pepper the method, and this caused the results to be 'odd', or partially incorrect, because some of the points were just getting copied as references(I guess? I think?) -- but it was still pretty nearly as fast as the C version. Now with the deepcopy calls added, the routine does it's job correctly, but it has incurred an extreme performance penalty, and now takes several seconds to do the same job. This seems like a pretty common job, but I'm clearly not doing it the pythonic way. How should I be doing this so that I still get the correct results but don't have to include deepcopy everywhere?

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• Setting up ehcache replication - what multicast settings do I need?

  - by Darren Greaves

  I am trying to set up ehcache replication as documented here: http://ehcache.sourceforge.net/EhcacheUserGuide.html#id.s22.2 This is on a Windows machine but will ultimately run on Solaris in production. The instructions say to set up a provider as follows: <cacheManagerPeerProviderFactory class="net.sf.ehcache.distribution.RMICacheManagerPeerProviderFactory" properties="peerDiscovery=automatic, multicastGroupAddress=230.0.0.1, multicastGroupPort=4446, timeToLive=32"/> And a listener like this: <cacheManagerPeerListenerFactory class="net.sf.ehcache.distribution.RMICacheManagerPeerListenerFactory" properties="hostName=localhost, port=40001, socketTimeoutMillis=2000"/> My questions are: Are the multicast IP address and port arbitrary (I know the address has to live within a specific range but do they have to be specific numbers)? Do they need to be set up in some way by our system administrator (I am on an office network)? I want to test it locally so am running two separate tomcat instances with the above config. What do I need to change in each one? I know both the listeners can't listen on the same port - but what about the provider? Also, are the listener ports arbitrary too? I've tried setting it up as above but in my testing the caches don't appear to be replicated - the value added in one tomcat's cache is not present in the other cache. Is there anything I can do to debug this situation (other than packet sniffing)? Thanks in advance for any help, been tearing my hair out over this one!

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• Advantages/disadvantages of Python and Ruby

  - by Seburdis

  I know this is going to seem a little like all the other python vs ruby question out there, but I'm not looking specifically to pick one over the other all the time. My question is, essentially, why would you use one language over the other when you are starting a new project? What features does ruby have that python doesn't that would make you decide on it for a given project? What about python over ruby? I was just recently thinking about the differentiation between the two languages because of Jamis Buck's "There is no magic, only awesome" series of articles (4 parts, available here) when I realized I really don't know enough about the two languages to know when to choose one over the other. I'm hoping to get objective answers from people who have experience with both languages, rather than just "python is better, ruby sucks" kind of responses. If you know of a feature in one language that doesn't exist in the other and is great in a certain situation, feel free to chime in and say why you think it's awesome. If you have another language comparable to these that you'd like to suggest pros/cons for, like groovy for example, that would be appreciated too. Some thing I know each language has going for it: Ruby: Awesome metaprogramming Great community Wide selection of Gems Rails Great code readability, usually MacRuby is great for native development on Mac without objc Amazing testing tools (cucumber, rspec, shoulda, autotest, etc.) Python: Whitespace indentation List comprehensions Better functional programming support? Lots of support on linux Easy_install isn't far from gems Great variety of libraries available

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• How to solve with using Flex Builder 3 and BlazeDS?

  - by Teerasej

  Hi, everyone. Thank you for interesting in my question, I think you can help me out from this little problem. I am using Flex builder 3, BlazeDS, and Java with Spring and Hibernate framework. I using the remote object to load a string from spring's configuration files. But in testing, I found this fault event like this: RPC Fault faultString="java.lang.NullPointerException" faultCode="Server.Processing" faultDetail="null" I have check the configuration in remote-config.xml and services-config.xml. But it looks good. There is some people talked about this problem around the internet and I think you can help me and them. I am using these environment: Flex Builder 3 BlazeDS 3.2.0 JBoss server Full stacktrace: [RPC Fault faultString="java.lang.NullPointerException" faultCode="Server.Processing" faultDetail="null"] at mx.rpc::AbstractInvoker/http://www.adobe.com/2006/flex/mx/internal::faultHandler()[C:\autobuild\3.2.0\frameworks\projects\rpc\src\mx\rpc\AbstractInvoker.as:220] at mx.rpc::Responder/fault()[C:\autobuild\3.2.0\frameworks\projects\rpc\src\mx\rpc\Responder.as:53] at mx.rpc::AsyncRequest/fault()[C:\autobuild\3.2.0\frameworks\projects\rpc\src\mx\rpc\AsyncRequest.as:103] at NetConnectionMessageResponder/statusHandler()[C:\autobuild\3.2.0\frameworks\projects\rpc\src\mx\messaging\channels\NetConnectionChannel.as:569] at mx.messaging::MessageResponder/status()[C:\autobuild\3.2.0\frameworks\projects\rpc\src\mx\messaging\MessageResponder.as:222]

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• Apache attack on compromised server, iframe injected by string replace

  - by Quang-Tuan Luong

  My server has been compromised recently. This morning, I have discovered that the intruder is injecting an iframe into each of my HTML pages. After testing, I have found out that the way he does that is by getting Apache (?) to replace every instance of <body> by <iframe link to malware></iframe></body> For example if I browse a file residing on the server consisting of: </body> </body> Then my browser sees a file consisting of: <iframe link to malware></iframe></body> <iframe link to malware></iframe></body> I have immediately stopped Apache to protect my visitors, but so far I have not been able to find what the intruder has changed on the server to perform the attack. I presume he has modified an Apache config file, but I have no idea which one. In particular, I have looked for recently modified files by time-stamp, but did not find anything noteworthy. Thanks for any help. Tuan. PS: I am in the process of rebuilding a new server from scratch, but in the while, I would like to keep the old one running, since this is a business site.

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• Android Web App : Position:fixed broken?

  - by StevenGilligan

  Hi all, I'm in the process of developping a Web Application for mobiles. I went with web applications because to me it seems a winning situation having to develop one application that could run also on iPhone / Windows Mobile / Palm etc. I started testing today after a few days of doing concepts, ideas and designs and what I wanted to do was have a menu that sticks at the bottom of the page. Exactly like the menu on the bottom in this iPhone application screenshot : http://farm4.static.flickr.com/3094/2656904921_1c54e93b4f.jpg Using CSS, I though it would be really easy to do this. Only using position:fixed; bottom:0; would have done the trick but I have found it doesn't behave the same on mobile browsers I tried to split my page in 2 sections : 1 would be a scrollable div (for the content) and the other one would be the bottom menu. Scrollable divs also do not work on Android. I also tried using frames with no luck either. Does anyone know of any way to re-create a menu that would stick to the bottom of a page for mobile phones? Thank you, Steven

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• Parsing multibyte string in PHP

  - by Petr Peller

  I would like to write a (HTML) parser based on state machine but I have doubts how to acctually read/use an input. I decided to load the whole input into one string and then work with it as with an array and hold its index as current parsing position. There would be no problems with single-byte encoding, but in multi-byte encoding each value does not represent a character, but a byte of a character. Example: $mb_string = 'žšcr'; //4 multi-byte characters in UTF-8 for($i=0; $i < 4; $i++) { echo $mb_string[$i], PHP_EOL; } Outputs: L ž L A This means I cannot iterate through the string in a loop to check single characters, because I never know if I am in the middle of an character or not. So the questions are: How do I multi-byte safe read a single character from a string in a performance friendly way? Is it good idea to work with the string as it was an array in this case? How would you read the input?

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• OpenPeak Flash app XMLSocket Security Problem

  - by Kira

  We're trying to create an app for OpenPeak. The Flash app will act as a client to a Java server on another computer on another domain. The Flash app client connects via XMLSocket. The Java Server uses ServerSocket to receive a request and send back a message. In order to trust the server, the Flash client needs a socket master policy file to tell it that the server comes from a trustworthy domain. According to an article on Adobe, when a connection has succeeded, the Flash client automatically requests the cross-domain policy or socket master policy file on port 843. Still, even when we implement it according to the tutorials and recommendations we have read, the Flash client continues to throw the following security error: SecurityErrorEvent type="securityError" bubbles=false cancelable=false eventPhase=2 text="Error #2048" We've tried logging the policy file request during testing to see if there was any call made to port 843. There was not. Interestingly, even without a policy file, the Flash client still manages to send the first data message to the server successfully. It's just when the server tries to send back a reply that the entire thing hangs for about 10 seconds before the security error above is displayed. Any ideas / suggestions?

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